Credit Suisse, Raiffeisen and Vontobel are handling the issue, worth 350 million to 450 million Swiss francs, he told an investor presentation.

Pricing will be based on five-year swaps for the bond, which will be callable after 5-1/3 years. More details are due within days.

The bond would be written off if the bank's regulatory core tier 1 capital ratio fell below 7 percent, an unlikely event equivalent to a loss of more than 400 million francs.

Vontobel, which has not posted an annual loss in the past 15 years, expects a core tier 1 ratio of 12.2 percent at the end of this year. ($1 = 0.9848 Swiss francs) (Reporting by Rupert Pretterklieber, Writing by Michael Shields; editing by Brenna Hughes Neghaiwi)